HP-97 card reader feeds cards OK, writes OK, but cannot read cards. HP displays "Error" each time I feed a card through.I changed gummy wheel to new O-rings from Mark Hoskins, cleaned the head and still no luck.Has anyone experienced a similar problem? What else can I check?

Since you replaced the o rings you had to remove the white pinch roller axle. There are two physical possibilities;

the o-rings are not the same Outer Diameter (OD)

the o-rings have the correct OD but the axle was not installed
in the same position as it was removed from.

The axle is assymetric which when turned in position will raise or lower the pinch roller thus raising or lowering the magnetic strip away from or towards the reader head. I have seen this incorrect height of the pinch roller to cause Read errors but not write errors.

Cheers, Geoff

This assumes the electronics are not a fault as in this case: capacitor